Examples for such a component can be found in documents DE 10 2012 014 620 A1 and WO 2014/126548 A1. The opening in the wall of the component which is covered by the perforated cover serves to the sound damping when exhaust gas flows through the component. Due to the (although low) gas flow rate through the opening, fewer resonances are generated by stationary waves within the component. Turbulent currents in the exhaust gas flow can furthermore be dampened and be converted into laminar currents, which reduce the proportion of high frequencies in the frequency spectrum.
The perforated cover may be a metal sheet provided with a large number of small openings. The perforation degree is in the order of 1 to a maximum of 10% of the entire surface of the cover, in particular in the range of 1 to 3%. Each single pore has an area size in the range of 0.02 to 2 mm2, preferably in the range of 0.04 to 1 mm2.
The perforated cover is usually welded to the wall of the exhaust-gas-ducting component. A reliable fastening with the desired high lifetime is thus obtained. However, it became apparent that high loads may act onto the perforated cover when thermal expansions occur.
The higher the difference of the thermal expansion coefficients is, the more critical is the effect of the loads of the perforated cover. One example for different thermal expansions are ferritic steel alloys that can be used for the exhaust-gas-ducting components, and austenitic steel alloys, which are used for the perforated cover.
The object of the invention is to develop the known component such that no difficulties occur in case of thermal expansions of the component and/or of the cover.